FIGURE 2.

Competitive association of [³H]mepyramine and unlabeled antihistamines to the H₁R. An homogenate of HEK293T cells transiently expressing the H₁R was incubated with a 2.4 nM concentration [³H]mepyramine in the absence or presence of 1 to 100-fold K_i concentrations of the respective unlabeled antihistamines for the indicated time at 25°C in 50 mM Na₂HPO₄/KH₂PO₄ pH 7.4. Results are shown for the unlabeled antihistamines mepyramine (A), doxepin (B), levocetirizine (C) and olopatadine (D). Representative graphs of ≥3 experiments are shown with mean ± SD of duplicate values (n = 2).